640944399 has 8 divisors (see below), whose sum is σ = 884061360. Its totient is φ = 412561856.

The previous prime is 640944391. The next prime is 640944407. The reversal of 640944399 is 993449046.

It is an interprime number because it is at equal distance from previous prime (640944391) and next prime (640944407).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 640944399 - 2³ = 640944391 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640944391) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3683502 + ... + 3683675.

It is an arithmetic number, because the mean of its divisors is an integer number (110507670).

Almost surely, 2^640944399 is an apocalyptic number.

640944399 is a deficient number, since it is larger than the sum of its proper divisors (243116961).

640944399 is a wasteful number, since it uses less digits than its factorization.

640944399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7367209.

The product of its (nonzero) digits is 839808, while the sum is 48.

The square root of 640944399 is about 25316.8797248002. The cubic root of 640944399 is about 862.1975522619.

The spelling of 640944399 in words is "six hundred forty million, nine hundred forty-four thousand, three hundred ninety-nine".